Number of (2n+1) X (2n+1) symmetric matrices each of whose rows is a permutation of 1..(2n+1).
A036981
Number of (2n+1) X (2n+1) symmetric matrices each of whose rows is a permutation of 1..(2n+1).
Terms
- a(0) =1a(1) =6a(2) =720a(3) =31449600
External references
- oeis: A036981